Supporting members for a hot cathode block



Se t. 13, 1966 w. DIETRICH 3,273,003

SUPPORTING MEMBERS FOR A HOT CATHODE BLOCK Filed Feb. 6, 1963 FIG] F/G3 F/GZ F/G.4

United States Patent 2 Claims. 61. 313-82) The present invention relates to an improved blockshaped cathode which may be heated either directly or indirectly and is intended for use as an electron source in an electron gun.

For emitting cathode currents of 100 ma. and more, it is already known to provide electron sources in the form of block-shaped hot cathodes. Such cathodes are usually installed in so-called electron guns which are connected to electron-beam apparatus, such as electron annealing or melting furnaces, welding apparatus, or the like for emitting electron beams for the respective purposes of the apparatus. Prior to this invention it has always been very difiicult to center these block-shaped cathodes accurately while they are in operation. This becomes necessary since even very small deviations from the central position of such electrodes cause serious difficulties in electron-optical respects. Furthermore, under the very high operating temperatures of, for example, 2300 C. it has been very difficult to supply the necessary current to such block-shaped hot cathodes of tungsten or tantalum. The supporting means of such a cathode must also be designed so as to take up the expansions of the cathode which are caused by the high operating temperatures so that no decentering of the cathode will occur. For attaining these objects, the supporting means for such a block-shaped cathode were previously provided in the form of several plane or corrugated sheet-metal strips of the same material as that of the cathode which were secured to the latter, for example, by welding, so as to extend in radial directions thereto. It has, however, been found that, because of the considerable changes in temperatures and stresses, such supporting means would break after the hot cathode had been in operation only for a relatively short time. Even during this time, these known supporting means could not take up the expansions of the cathode block uniformly. In consequence of this, the cathode had to be frequently exchanged and newly centered. This is, however, always a very difficult procedure, especially also in view of the fact that the electron guns in which such cathode are used must operate under a vacuum which must always be reestablished after each exchange or centering of the cathode. Obviously, this also involves considerable sealing diflicult-ies.

It is an object of the present invention to provide very simple means to overcome the above-mentioned difficulties in the use of directly or indirectly heated blockshaped hot cathodes serving as electron source in electron guns. According to the invention, this is attained by securing two or more supporting rods to the blockshaped cathode and in a manner so as to extend tangentially thereto. According to a preferred embodiment of the invention, several--for example, fourgrooves are cut or milled tangentially into the cathode and a sup- 3,273,003 Patented Sept. 13, 1966 port-ing rod of a corresponding cross-sectional shape is inserted into each of these grooves. These supporting rods may be used at the same time as current leads of the cathode.

This tangential arrangement of the supporting rods in tangential grooves in the peripheral surface of the cathode block has the advantage that the expansions of the latter under the high operating temperatures are taken up uniformly by the supporting rods without any danger that the cathode will thereby be decentered. This manner of connecting the supporting rods to the cathode block in tangential grooves also insures a very reliable supply of the high cathode current to the cathode block. The bending stresses which are exerted upon the supporting rods in the grooves when the cathode expands under the heat of the operation are very small. There is no danger of breakage of the supporting rods even after an operation of hours and more, and there is no longer any need for frequent exchanges and new centering of the cathodes as previously required. Another very important advantage which is attained by the invention is the fact that the entire unit consisting of the block-shaped cathode and the supporting rods is composed of very simple parts and may be very easily assembled and installed in an electron gun in which it will then be immediately centered and also remain centered during the operation.

The features and advantages of the present invention as described above will also be evident from the following drawings, in which:

FIGURES l and 2, respectively, show a plan view and a cross section of a block-shaped hot cathode of the conventional construction; while FIGURES 3 and 4, respectively, show a plan view and a cross section of a block-shaped hot cathode according to the invention.

According to the conventional construction of a blockshaped hot cathode 1 for an electron gun, as illustrated in FIGURES 1 and 2, a plurality, for example, four, corrugated sheet-metal strips 2 which extend in radial directions to the cathode 1 are welded thereto.

According to a preferred embodiment of the invention, as illustrated in FIGURES 3 and 4, the block-shaped hot cathode 3 is provided with four tangential grooves which are either cut or milled into the peripheral surface thereof. Into these grooves, supporting rods 4 are fitted, the free ends of which are then clamped in conventional holding means.

Although in many cases two or three supporting rods 4 may be sufiicient, four of them are usually preferred.

Although my invention has been illustrated and described with reference to the preferred embodiment thereof, I wish to have it understood that it is in no way limited to the details of such embodiment, but is capable of numerous modifications within the scope of the appended claims.

Having thus fully disclosed my invention, What I claim 1. Means for centrally mounting a hot cathode block in an electron gun comprising, a pair of opposed diametrically spaced straight parallel grooves formed in the periphery of said cathode block, and a pair of similar straight rods, one of said rods being disposed in one of said grooves in frictional engagement with the bottom and side walls of said one of said grooves and extending outwardly therefrom in one direction parallel to the said bottom wall of the said one of said grooves, and the other of said rods being disposed in the other of said grooves in frictional engagement with the bottom and side walls of the said other of said grooves and extending outwardly therefrom parallel to the said bottom wall of the said other of said grooves in a direction opposite to the direction in which the said one of said rods extends outwardly from the .said one of said grooves, the outer ends of said rods being adapted to be secured in fixed position to said electron gun, said mounting means being operative to compensate for the expansion or contraction of said cathode block due to temperature changes of said cathode block during operation.

2. A mounting means for a hot cathode block as defined by claim 1 in which another pair of opposed diametrically spaced straight parallel grooves are formed in the periphery of said cathode perpendicular to said pair of grooves, and in which a second pair of similar straight rods are mounted in said another pair of grooves in a manner similar to the mounting of said pair of rods in said pair of grooves, and the outer ends of said another pair of rods being adapted to be secured in fixed position to said electron gun.

References Cited by the Examiner UNITED STATES PATENTS JOHN W. HUCKERT, Primary Examiner.

A. I. JAMES, Assistant Examiner. 

1. MEANS FOR CENTRALLY MOUNTING A HOT CATHODE BLOCK IN AN ELECTRON GUN COMPRISING, A PAIR OF OPPOSED DIAMETRICALLY SPACED STRAIGHT PARALLEL GROOVES FORMED IN THE PERIPHERY OF SAID CATHODE BLOCK, AND A PAIR OF SIMILAR STRAIGHT RODS, ONE OF SAID RODS BEING DISPOSED IN ONE OF SAID GROOVES IN FRICTIONAL ENGAGEMENT WITH THE BOTTOM AND SIDE WALLS OF SAID ONE OF SAID GROOVES AND EXTENDING OUTWARDLY THEREFROM IN ONE DIRECTION PARALLEL TO THE SAID BOTTOM WALL OF SAID ONE OF SAID GROOVES, AND THE OTHER OF SAID RODS BEING DISPOSED IN THE OTHER OF SAID GROOVES IN FRICTIONAL ENGAGEMENT WITH THE BOTTOM AND SIDE WALLS OF THE SAID OTHER OF SAID GROOVES AND EXTENDING OUTWARDLY THEREFROM PARALLEL TO THE SAID BOTTOM WALL OF THE SAID OTHER OF SAID GROOVES IN A DIRECTION OPPOSITE TO THE DIRECTION IN WHICH THE SAID ONE OF SAID RODS EXTENDS OUTWARDLY FROM THE SAID ONE OF SAID GROOVES, THE OTHER ENDS OF SAID RODS BEING ADAPTED TO BE SECURED IN FIXED POSITION TO SAID ELECTRON GUN, SAID MOUNTING MEANS BEING OPERATIVE TO COMPENSATE FOR THE EXPANSION OR CONTRACTION OF SAID CATHODE BLOCK DUE TO TEMPERATURE CHANGES OF SAID CATHODE BLOCK DURING OPERATION. 